It is highly desirable for tires to have good wet skid resistance, low rolling resistance, and good wear characteristics. It has traditionally been very difficult to improve a tire's wear characteristics without sacrificing its wet skid resistance and traction characteristics. These properties depend, to a great extent, on the dynamic viscoelastic properties of the rubbers utilized in making the tire.
In order to reduce the rolling resistance and to improve the treadwear characteristics of tires, rubbers having a high rebound have traditionally been utilized in making tire tread rubber compounds. On the other hand, in order to increase the wet skid resistance of a tire, rubbers which undergo a large energy loss have generally been utilized in the tire's tread. In order to balance these two viscoelastically inconsistent properties, mixtures of various types of synthetic and natural rubber are normally utilized in tire treads.
Tires are sometimes desired with treads for promoting traction on snowy surfaces. Various rubber compositions may be proposed for tire treads. Here, the challenge is to reduce the cured stiffness of such tread rubber compositions, as indicated by having a lower storage modulus G′ at −20° C., when the tread is intended to be used for low temperature winter conditions, particularly for vehicular snow driving.
It is considered that significant challenges are presented for providing such tire tread rubber compositions for maintaining both their wet traction while promoting low temperature (e.g. winter) performance.